This invention relates to continuous hot-stretching apparatuses for giving a low relaxation characteristic to steel cables such as wire ropes and steel cables for prestressed concrete.
The hot-stretching process for steel cable, in general, involves heating a steel cable at a low temperature while applying a tension to the steel cable, which may cause a permanent elongation therein. Heretofore, such a steel cable is fabricated by a stranding machine provided separately, and then the steel cable is subjected to the hot-stretching treatment by the hot-stretching apparatus. Accordingly, the conventional method is disadvantageous in that it takes many man-hours for the conveyance of work between work stations and for work preparation, and during the period of starting the continuous hot-stretching apparatus a part of the cable lying between the heat treatment equipment and the winding machine cannot be subjected to heat treatment. Moreover, when the apparatus is stopped a part of the cable lying between the cable supplying means and the heat treatment equipment cannot be subjected to heat treatment, all of which leads to a poor yield and accordingly to an uneconomical operation.